1. (Field of the Invention)
This invention relates to an adhesive composition suitable for the production of a multilayered laminated body, and a laminated body using the above-mentioned adhesive composition.
More specifically, the present invention relates to a composition having excellent adhesiveness to a styrene-type resin layer and a layer of a saponified product of ethylene/vinyl acetate copolymer, and a laminated body equipped with a styrene-type resin layer, an adhesive composition layer, and a layer of a saponified product of ethylene/vinyl acetate copolymer.
2. (Description of the Prior Art)
Since a saponified product of an olefin/vinyl acetate copolymer (to be abbreviated as EVOH) typified by a saponified product of ethylene/vinyl acetate copolymer has excellent gas-barrier property, oil resistance and mechanical strength, but has high water permeability, it has a defect of being unable to be used singly as a food wrapping film or a molded container in which water is contained.
As a method of improving this defect, it has been proposed to laminate a styrene-type resin (to be abbreviated as PS) or a polyolefin-type resin having excellent water resistance. But since these resins do not contain a polar group, even when EVOH is directly laminated on the above resins, an interlayer adhesive force is very small and the resulting product cannot withstand practical use.
Various methods are available to improve the above defects. For example, methods of using a composition comprising an ethylene/vinyl acetate copolymer (to be abbreviated as EVA) and a tackifier are known (Japanese Laid-Open Patent Publication No. 129271/1978, Japanese Laid-Open Patent Publication No. 147733/1978, and Japanese Laid-Open Patent Publication No. 10384/1979).
Furthermore, Japanese Patent Publication No. 67813/1988 discloses a composition comprising an ethylene/vinyl acetate copolymer, a modified polyolefin copolymer, and a tackifier.
Japanese Laid-Open Patent Publication No. 72931/1993 discloses a composition comprising an ethylene/.alpha.-olefin copolymer, a modified polyolefin copolymer and a tackifier.
However, in the field of adhesives, a further increase of adhesive force is required between a styrene-type resin and a saponified layer of an ethylene/vinyl acetate copolymer, and an increase in after-processability of an adhered laminated body is also required. The after-processability of the adhered laminated body means that when the laminated body is molded into a cup or a tray, an excellent adhesive force should be maintained, and when cutting is carried out, the cut portion can be cut sharply without threading or peeling.
Conventional adhesive compositions may exhibit excellent properties, but are not satisfactory in such a requirement.